The continuing miniaturization trend in portable equipment requires more compact, high-efficiency DC-DC converters to maximize battery power that has been stretched to the limit by added device functionality. Designing smaller DC-DC converters hinges on reducing the size of the choke coil, its main and largest component. However, reducing the size of the wire-wound inductor (functioning as a choke coil to prevent or limit AC while allowing DC to flow) increases resistance and reduces the efficiency of the DC-DC converter. For this reason, it is very difficult to reduce the size of an inductor while maintaining the lower-resistance characteristics of larger components.
TAIYO YUDEN responded to this design challenge by improving the round drum/sleeve core technology used by conventional inductor designs. The company developed a unique sleeveless square-core winding that successfully eliminated all wasted space and thickened the lead wire inside the inductor to achieve the lowest possible DC resistance. As a result, the company was able to develop a compact, high-efficiency choke coil for DC-DC converter applications that offered a 50 percent reduction in surface area compared to conventional inductors, while at the same time providing a minimal level of DC resistance (RDC).